Television apparatus



April 93 F. scHRO ER j 1,996,492

TELEVISION APPARATUS Filed Jan. 5, 1932 RECEIVER AMPLIFIER RECEIVERAMPLIFIER INVENTQR FRITZ SCHROT R- ATfNEY constructed at the receivingpoint Patented Apr. 2, 1935' PATENT OFFICE TELEVISION Fritz Schriiter,Berlin, Telefunken Gesellsch APPARATUS Germany, assignor to aft fiirDrahtlose Telegraphic in. b. H., Berlin, Germany, a corporation ofGermany Application January 5,

1932, Serial No. 584,788

In Germany January 6, 1931 1 Claim.

The present invention relates to television receiving apparatus and isdirected principally to a method and means by which the effectiveintensity and brilliance of the electro-optical image may be increased.

It is known in the prior art that the picture screen of a televisorreceiver may be provided with a phosphorescent substance for the purposeof converting or shifting the blue, violet and ultraviolet constituentsof light radiation, which, while abundant in energy, are not veryconspicucus in visual respect, into a physiologically brighter or moreluminous spectral range, and further of insuring a lower blending orcoalescence frequency caused by the after-glow of the phosphorus. Aswill be seen upon closer examination, this latter aim is usuallyunattained in any system of the prior art, for when choosing a sort ofphosphorus whose after-glow period covers a period being longer than thebuilding-up period of an individual television picture, blurred contoursare produced in the reproduction of animated pictures. Whenever arapidly decaying phosphorus is used no decrease in the physiologicflicker efiect may be expected because of the impairment of thecinematographic sector relation.

The principal purpose and object of the present invention thus is toutilize effectively the properties of phosphorus for securing areduction in flicker by the aid of a suitable process.

With this end in view there is used the prop erty of most grades orkinds of phosphorus first to store up energy by the action of primaryirradiation or illumination, and then, subsequent ly, such stored-upenergy may be released or given off by irradiation through the use ofinvisible rays. These invisible rays are principally infra-red rayswhich act in a practically instantaneous manner in the shape of luminousemission, that is, the extinction so-called of phosphorus.

The invention will be understood best by referring to the accompanyingdrawing which forms a part of this disclosure. In the drawing, Fig, 1shows one form of the invention using a mirror-wheel as a scanningelement; and Fig. 2 shows a modified form wherein a cathode ray imagere-creating system is utilized.

To refer now to the form of the invention as set forth by themirror-wheel type of televisor of Fig. 1, it is seen that the lightissuing from a luminous source I of constant intensity is focused bymeans of a condenser lens system 2 upon a Kerr cell and associatedpolarizing and analyzing Nicol prisms 3. The Kerr cell electrodesconnect with the signal receiver sothat the light from source I ismodulated in the cell in accordance with the incoming picture impulsesor signals and then is projected by the aid of an objective lens system4 and a rotary mirror-wheel 5, or equivalent scanning ture re-creationscreen 6 upon which it is spread in a surface by virtue of the rotationof the mirror-wheel or scanning element.

The picture projection screen 6 is coated with phosphorous of a sorthaving the capability of accumulating luminous energy whenirradiatphorus of the said sort may be mentioned zinc sulfide comprisinga heavy metal.

According to the present invention, after a suitable length of time,preferably after a period equalling in time that required to re-buildhalf a picture a more or less suddenly occurring extinction of thepicture points scanned or swept by the light rays re-creating theelectro-optical picture by invisible radiation is produced, forinstance, infra-red rays. For this purpose another mirror-wheel l ismounted upon the same spindle as the mirror-wheel 5, the formerpresenting a phase shifting angle 180 degrees with reference to thelatter. The supplementary mirror-wheel 1 causes a ray of infra-redradiation issuing from a suitable radiation source 8 which is focused byan the mirror-wheel 1 to scan the picture projection screen 6. In frontof the radiation source 8, if desired, a suitable filter l0 could bemounted in the manner indicated.

What is evidently attained by an arrangement of the kind hereinbeforedisclosed is that each picture point or unit during each rotation of themirror-wheel is rendered active twice or, in other words, the number ofpicture changes required to prevent the impression of a flicker isdiminished or, to be more precise, about halved.

In case it should be found that in the selection of a definite kind ofphosphorus the extinction period inherent in the sweeping over thesurface of the infra-red spot is too short, this condition may beremedied either by choosing the extinctive infra-red spot substantiallylarger than the picture re-creating visible spot or else by using a moreor less wide infra-red light line or stripe for the purpose ofextinction. The infra-red light line trails behind the motion of thepicture re-creating luminous spot over the picelement, upon the pic- 9objective 9 upon ture projection screen as above described. The width ofthis line, if required, may cover several picture lines.

From what has been above described, it will be seen that therequirements to be made of the precision and the optical qualities ofthe auxiliary mirror-wheel are very small indeed, so that a relativelycrude and cheap form of construction will suffice.

The principle here described by the aid of a mirror-wheel televisionreceiver may be readily applied also to picture scanning devices ofdifferent types such as has been suggested by the form of the inventionshown by Fig. 2. This embodiment is predicated upon the use of a Braunor cathode ray tube acting as the television receiver element, and theassumption has here been made that the infra-red extinction is insured,as above indicated, by the aid of a line or stripe of infra-redradiation.

Similarly to the construction shown by Fig. 1, the cathode ray or Brauntube l2 may be connected with the receiver so that incoming signalscontrol the ray intensity as shown, for example, by U. S. Patent#1,470,696 through the use of grid control. The cathode ray I5 issuitably deflected by electrostatic or electro-magnetic fields l3 and I4so as to cause the image points to be traced on the fluorescent end walll5 of the tube l2.

After the electro-optical image has been formed on the end wall l5 ofthe tube I2, the infra rays from a source I1 may be caused to sweep overthe picture screen by the agency of a tilting or oscillating mirror l8in a way readily understood from the drawing.

Care must be taken so that the motion of the tilting mirror l8 will bein synchronism with the period of the electron-ray motion inside theBraun tube l2. This is accomplishable in a particularly simple manner ifthe deflector potenaccesses tials acting upon the cathode ray pencil areobtained from a tone-frequency generator equipped with rotating membersas has been disclosed in U. S. patent application of August Karolus,8erial No. 545,965, flled June 22, 1931. The motion of the tiltingmirror need then to be made dependent only upon the speed of rotation ofthe generator. It will be understood that in lieu of the saidoscillatory mirror recourse may be had also to other similarly operatingmeans for the deflection of the radiations, such as a tilting prism or amirror-studded drum.

Many modifications will suggest themselves and become apparent to thoseskilled in the art to which the invention relates and it is. therefore,intended that the following claim shall be construed in the broad andgeneric sense to cover all such forms of the invention as would suggestthemselves.

Having now described my invention, what I claim and desire to secure byLetters Patent is the following:

In a television system, a cathode ray tube provided at one end with aphosphorescent screen, means for receiving signals representative 0!fluctuating light intensities on successive elemental areas of a recordsurface, means tor producing on said screen in accordance with saidreceived signals sustained light spots or varying intensityrepresentative of each elemental area of a received picture, and anoscillatory means synchronized with the said light spot control meansfor traversing each elemental area of said screen at a time periodsubstantially midway between the time period of recurrence of controlledlight illumination of each of said elemental screen areas by invisiblelight waves for extinguishing the fluorescent eflect produced upon saidscreen by said initial illumination.

FRITZ scrmo'rsa.

